Vapour turbine

Description

[0001] The present invention relates to a vapour turbine which can be used for obtaining energy from geothermal vapours.

[0002] Vapour turbines which operate with geothermal vapours come into contact with aggressive and/or corrosive substances for the components of the turbine itself.

[0003] Even small quantities of aggressive substances such as chlorides and sulfides, cause the corrosion of the vapour turbine components, such as rotor blades, stator blades and sealing laminas.

[0004] The materials currently used for vapour turbine components are martensitic stainless steels which are strongly subject to corrosion phenomena on the part of aggressive and/or corrosive agents.

[0005] The corrosion is particularly high in the transition area between overheated vapour and damp vapour (Dew Point).

[0006] In this area, the solid particles contained in the geothermal vapour form large deposits on the surface of the blades.

[0007] During the functioning of the turbine, the deposits accelerate the corrosion process under way, due to the increase in localized concentration of corrosive agents such as chlorides and sulfides.

[0008] Corrosion of the turbine components jeopardizes the correct functionality of the turbine itself as well as the preventive maintenance plan programmed for it.

[0009] In order to reduce maintenance interventions and consequently also substitution of the components themselves, the geothermal vapours containing aggressive substances in a higher quantity than a predetermined percentage, are "washed" with water.

[0010] This reduces the concentration of aggressive substances present in the geothermal vapours.

[0011] A first disadvantage is that the washing operations of geothermal vapours causes an increase in the running and maintenance costs of the piant, also increasing its complexity.

[0012] Another disadvantage is that upon washing the vapour, the enthalpy available at the turbine inlet is reduced and consequently the useful work of the turbine itself is reduced.

[0013] An objective of the present invention is to provide a vapour turbine operating with overheated geothermal vapours normally containing corrosive agents which avoids the washing of said geothermal vapours.

[0014] A further objective is to provide a vapour turbine operating with overheated geothermal vapours, which has a high conversion efficiency of the energy available at the inlet.

[0015] Another objective to provide a vapour turbine which operates with overheated geothermal vapours and which has a high useful life.

[0016] Yet another objective to provide a vapour turbine operating with geothermal vapours, containing corrosive agents, having reduced maintenance costs.

[0017] According to the invention, there is provided a vapour turbine operating with geothermal vapours containing corrosive agents such as chlorides and/or sulfides in particular, characterized in that it comprises a series of stator blades made of a nickel alloy containing a quantity of nickel ranging from 54% to 58% by weight to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of stator blades and said vapour turbine .

[0018] The nickel alloy may be a nickel-chromium-molybdenum alloy and may comprise a quantity of chromium ranging from 21% to 23% by weight, a quantity of molybdenum ranging from 12% to 14.5% by weight.

[0019] The turbine may comprise a series of sealing laminas made of said nickel alloy to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of sealing laminas and said vapour turbine.

[0020] The turbine may comprise a series of rotor blades made of a nickel-chromium-molybdenum-niobium alloy to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of rotor blades and of said vapour turbine.

[0021] The nickel-chromium-molybdenum-niobium alloy preferably comprises a quantity of nickel ranging from 55% to 59% by weight, a quantity of chromium ranging from 19% to 22.5% by weight, a quantity of molybdenum ranging from 7.0% to 9.5% by weight, a quantity of niobium ranging from 2.75% to 4% by weight.

[0022] The invention also includes the use of a series of stator blades made of a nickel-chromium-molybdenum alloy for a vapour turbine operating with geothermal vapours containing corrosive agents, such as chlorides and/or sulfides in particular, to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of stator blades.

[0023] The characteristics and advantages of a vapour turbine operating with geothermal vapours will appear more evident from the following illustrative and non-limiting description of the present invention.

[0024] According to the present invention, a vapour turbine is provided, operating with geothermal vapours containing aggressive or corrosive agents such as chlorides and/or sulfides in particular.

[0025] The vapour turbine comprises a series of stator blades made of a nickel alloy containing a quantity of nickel ranging from 54% to 58% by weight to avoid the washing of said geothermal vapours, at the same time maintaining a high useful life of said series of stator blades and said vapour turbine.

[0026] It is advantageously possible to convert, by means of said turbine, a greater quantity of energy as the non-washed geothermal vapours have a higher enthalpy with respect to washed geothermal vapours.

[0027] Said turbine is advantageously particularly efficient for geothermal vapours containing a quantity of chlorides higher than 2 ppm, avoiding the washing thereof.

[0028] Said nickel alloy is preferably a nickel-chromium-molybdenum alloy.

[0029] Said nickel alloy preferably comprises a quantity of chromium ranging from 21 % to 23% by weight, a quantity of molybdenum ranging from 12% to 14.5% by weight.

[0030] Said nickel alloy is preferably a super-alloy of nickel known commercially as HASTELLOY C22.

[0031] Said turbine preferably also comprises a series of sealing laminas made of said nickel alloy, in particular made of HASTELLOY C22.

[0032] This is to avoid the washing of said geothermal vapours, at the same time maintaining a high useful life of said series of stator blades and sealing laminas and said vapour turbine.

[0033] Said turbine preferably also comprises a series of rotor blades made of a nickel-chromium-molybdenum-niobium alloy to avoid the washing of said geothermal vapours, at the same time maintaining a high useful life of said series of rotor blades and the vapour turbine itself.

[0034] Said nickel-chromium-molybdenum-niobium alloy preferably comprises a quantity of nickel ranging from 55% to 59% by weight, a quantity of chromium ranging from 19% to 22.5% by weight, a quantity of molybdenum ranging from 7.0% to 9.5% by weight, a quantity of niobium ranging from 2.75% to 4% by weight.

[0035] Said nickel-chromium-molybdenum-niobium alloy is preferably a nickel super-alloy, commercially known as INCONEL 725.

[0036] According to a further aspect of the present invention, the use of a series of stator blades made of a nickel-chromium-molybdenum alloy, in particular made of HASTELLOY C22, for a vapour turbine operating with geothermal vapours containing corrosive agents, such as chlorides and/or sulfides in particular, is evident, to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of stator blades.

[0037] It can thus be seen that a vapour turbine according to the present invention achieves the objectives specified above.

Claims

1. A vapour turbine operating with geothermal vapours containing corrosive agents such as chlorides and/or sulfides in particular, characterized in that it comprises a series of stator blades made of a nickel alloy containing a quantity of nickel ranging from 54% to 58% by weight to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of stator blades and said vapour turbine .

2. The turbine according to claim 1, characterized in that said nickel alloy is a nickel-chromium-molybdenum alloy.

3. The turbine according to claim 1 or 2, characterized in that said nickel alloy comprises a quantity of chromium ranging from 21% to 23% by weight, a quantity of molybdenum ranging from 12% to 14.5% by weight.

4. The turbine according to any of the claims from 1 to 3, characterized in that it comprises a series of sealing laminas made of said nickel alloy to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of sealing laminas and said vapour turbine.

5. The turbine according to any of the claims from 1 to 4, characterized in that it comprises a series of rotor blades made of a nickel-chromium-molybdenum-niobium alloy to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of rotor blades and of said vapour turbine.

6. The turbine according to claim 4, characterized in that said nickel-chromium-molybdenum-niobium alloy preferably comprises a quantity of nickel ranging from 55% to 59% by weight, a quantity of chromium ranging from 19% to 22.5% by weight, a quantity of molybdenum ranging from 7.0% to 9.5% by weight, a quantity of niobium ranging from 2.75% to 4% by weight.

7. Use of a series of stator blades made of a nickel-chromium-molybdenum alloy for a vapour turbine operating with geothermal vapours containing corrosive agents, such as chlorides and/or sulfides in particular, to avoid the washing of said geothermal vapours, maintaining a high useful life of said series of stator blades.